Sale #1:

https://backpack.tf/profiles/76561198030343929#!/compare/1553731200/1553817600

Sold for 20 keys and 10 ref.

20 keys

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Sale #2:

https://marketplace.tf/items/209;15;u702;w4;pk310

Sold for $45.

$45 / $1.80 = 25 keys

25 keys

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Sale #3:

https://backpack.tf/profiles/76561198798888727#!/compare/1549238400/1549324800

Sold for a Fountain of Delight Taunt: Flippin' Awesome (10 keys) and Strange Festivized Specialized Killstreak Australium Black Box (11 keys).

21 keys

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Sale #4:

https://backpack.tf/profiles/76561198073438708#!/compare/1550102400/1550188800

Unsure.

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Sale #5:

https://backpack.tf/profiles/76561198073438708#!/compare/1553472000/1553558400

Sold for 20 keys and 17 ref.

20 keys

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Minis:

Strange Specialized Killstreak Australium Black Box:

https://bot.tf/stats/item?def=228&q=11&ef=&craft=1&aus=1&ks=2

11 keys

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Fountain of Delight Taunt: Flippin' Awesome:

https://backpack.tf/profiles/76561198317903441#!/compare/1551135600/1551222000

Sold for ~10 keys.

10 keys

Sales:

20, 20, 21, 25. Going with 20 - 25 keys.